Background and objectives

Integrated Ocean Drilling Program Site U1314 is located on the southern Gardar Drift in a water depth of 2820 m (Fig. F1). Seismic data for positioning of Site U1314, including multichannel seismic profiling (Fig. F2), 3.5 kHz high-resolution profiling (Fig. F3), and a SeaBeam survey, were collected during the Knorr KN166-14 cruise (principal investigator: Greg Mountain) in summer 2002. The high-quality seismic profiles indicate that Site U1314 is optimally positioned in a thick (>700 ms two-way traveltime), well-stratified sediment pile (Fig. F2).

On the crest of the Gardar Drift, a 33 m core (MD99-2253) was collected by the Marion Dufresne in 1999 (56°21.78′N, 27°48.95′W; water depth = 2840 m). This is close to the location of Site U1314 (Fig. F1). It lies on oceanic crust close to Anomaly 10 (~30 Ma), and the total sediment thickness is ~600 m. Piston Core MD99-2253 revealed a high sedimentation rate of ~9 cm/k.y. for the last glacial cycle and produced well-defined planktonic δ18O and geomagnetic paleointensity records (Channell et al., 2004).

During Ocean Drilling Program (ODP) Leg 162, Site 983 (60°24.2′N, 23°38.4′W) and Site 984 (61°25.5′N, 24°4.9′W) were drilled south of Iceland on the northern part of the Gardar and Bjorn Drifts, respectively (Fig. F1) (Jansen, Raymo, Blum, et al., 1996). These sites have mean Pleistocene sedimentation rates in the 10–15 cm/k.y. range and have produced high-resolution climatic (Fig. F4) and geomagnetic records (e.g., Raymo et al., 1998; Channell et al., 1998; Flower et al., 2000). Sites 983 and 984, however, are located outside the main ice-rafted debris (IRD) belt (sensu Ruddiman, 1977) and do not contain a robust detrital carbonate (Heinrich layer) signal. Furthermore, both sites are at shallower water depths (<2000 m) than Site U1314 and therefore monitor intermediate water but not North Atlantic Deep Water (NADW). Thus, the location of Site U1314 in the southern part of the Gardar Drift has been selected for the following objectives:

The location of Site U1314 is close enough to the IRD belt to record the Heinrich-type detrital layers that monitor ice sheet instability.

The water depths at Site U1314 (2820 m) and the ability to derive a benthic stable isotope record from this region (see Chapman and Shackleton, 1999) will allow ice sheet–ocean interaction to be placed on a benthic isotopic record, and carbon isotope data will allow high-resolution monitoring of NADW.

Sedimentation rates are as high as needed for the proposed high-resolution studies.

Good preservation of foraminifers, nannofossils, and diatoms, and the potential for paleomagnetic and isotopic age control, means that the environmental record comprising sea-surface and bottom water characteristics and detrital (Heinrich-type) stratigraphy can be integrated into a paleointensity-assisted chronostratigraphy.